Note for H2 Chemistry : it is a non-issue, because Cambridge
only cares that you write the symbol for it (ie. 298K), and not
spell it out (eg. 298 Kelvins / 298 kelvins / 298 Kelvin / 298
kelvin).
Are there reasons for the discrepancies in absolute temp
units - Kelvin vs. kelvins vs. degrees Kelvin?
Before 1968, the units for absolute temperature were described
as "degrees Kelvin" or "degrees absolute." After that, the SI
system got rid of the idea of "degree" for absolute temperature, so
the new unit should apparently be expressed as a "kelvin" (with
lowercase k) and abbreviated simply "K" (without the degree sign).
Also, official SI conventions suggest that not only should the unit
name be lowercase, but it should be pluralized as other units would
be: "Il en résulte que la température thermodynamique du point
triple de l’eau est égale à 273,16 kelvins exactement, Ttpw =
273,16 K." Or, in English: "It follows that the thermodynamic
temperature of the triple point of water is exactly 273.16 kelvins,
Ttpw = 273.16 K."
Despite the official SI usage, however, it seems that there are
still a variety of conventions in use. Many of the questions on
this forum, for example, use Kelvin (with a capital) instead of
kelvin in referencing the unit. Also, it appears that the plural
usage is somewhat mixed in the physics literature: something like
"200 kelvins" occurs, but more rarely than "200 kelvin" or even
"200 Kelvin." The NIST guidelines do not list the kelvin as an
exception to the normal pluralization rules: "the following plurals
are irregular: Singular — lux, hertz, siemens; Plural — lux, hertz,
siemens." On the other hand CERN's writing guidelines suggest that
there is an exception: "And note that it is always kelvin, even
when plural (not kelvins or degrees kelvin)."
Given all of this, here is my question: Is the SI standard
actually to pluralize kelvins, as would be suggested from the
quotations from the official SI guides above? Is this officially
stated anywhere in some standards organization's guidelines? Or, is
there some rationale given somewhere for the continued use of
plural "kelvin" (as in the CERN guidelines) or even "Kelvin" (with
an apparently anomalous capital)?
Or, is it -- as I suspect -- just a failure to treat the kelvin
as an actual SI unit, despite the redefinition from "degrees
Kelvin" to "kelvins" that happened decades ago? (Perhaps we just
dropped the "degree" but effectively still treat it the same way as
Celsius or Fahrenheit?)
http://physics.stackexchange.com/questions/114079/are-there-reasons-for-the-discrepancies-in-absolute-temp-units-kelvin-vs-kelv
